Autologous serum skin test

What is autologous? serum skin test?

The autologous serum skin test is a research test to autoimmune urticaria, which is a type of chronic urticaria. It is carried out in specialized centers for some patients with chronic urticaria.

Normal immunoglobulin-ME antibodies (IgE) activates IgE receptors (FceRI) in mast cells and basophils. These cells release histamine, an important mediator in allergic responses. Autoimmune urticaria is due to autoantibodies that bind to these receptors or to the IgE antibodies themselves. This causes inappropriate activation of mast cells and basophils and the release of histamine.

Autologous serum skin tests detect circulating autoantibodies, indicating an autoimmune origin in some patients with chronic urticaria.

When are autologous serum skin tests done?

Inducible Chronic urticaria can be detected when a certain stimulus causes scarring, such as cold air in cold urticaria or scratching the skin in dermographism.

Spontaneous or ordinary chronic urticaria may not have an obvious trigger. The autologous serum skin test can be a useful diagnostic tool because it confirms such cases due to autoimmunity. If the test is negative, it is considered chronic spontaneous urticaria. idiopathic, that is, it has no known cause.

Details of the procedure.

The patient should stop taking antihistamines 2–3 days before the autologous serum skin test, to ensure that their hives are active at the time of the test. Immunosuppressive agents can also be stopped for up to 3 months before the test.

The test should not be done on an area of skin that has had cure in the last 24 hours

• Two milliliters from the patient. venous Blood is drawn, allowed to clot for 30 minutes, and then centrifuged to extract serum from the blood.
• A small sample of serum is injected into the lower part of the patient's forearm.
• Histamine is injected as positive controland saline Water is injected as a negative control.
• There should be 5 cm gaps between each injection site.
• The response is recorded after 30 minutes.

A positive result occurs when the bump formed where the serum is injected has a diameter that is at least 1.5 mm larger than the saline solution.

What are the benefits of autologous serum skin tests?

Autologous serum skin tests are relatively reliable, with a sensitivity of 70% and a specificity of 80%. It is inexpensive and easy to administer.

What are the disadvantages of autologous serum skin tests?

Autologous serum skin tests should be performed by an experienced investigator; Poor technique can lead to false positive or false negative results.

The test is not standardized, with several methods described in the literature and different criteria for a positive result.

Positive results can occur in patients who do not have chronic urticaria, for example:

• Patients with autoimmune thyroid disease.
• Up to 80% of children with allergic or non-allergic respiratory symptoms.
• Drugs such as antihistamines, corticosteroids, and immunosuppressive medications.

Although a positive autologous serum skin test may indicate autoimmune urticaria, it does not reflect the severity of the disease.

What are the side effects of autologous serum skin tests?

Side effects are limited to injection site scars.